The present invention relates generally to the treatment of end stage renal disease. More specifically, the present invention relates to methods and apparatus for performing peritoneal dialysis.
It is known to use dialysis to support a patient whose renal function has decreased to the point where the kidneys no longer sufficiently function. Two principal dialysis methods are utilized: hemodialysis; and peritoneal dialysis.
In hemodialysis, the patient's blood is passed through an artificial kidney dialysis machine. A membrane in the machine acts as an artificial kidney for cleansing the blood. Because it is an extracorporeal treatment that requires special machinery, there are certain inherent disadvantages with hemodialysis.
To overcome the disadvantages associated with hemodialysis, peritoneal dialysis was developed. Peritoneal dialysis utilizes the patient's own peritoneum as a semi-permeable membrane. The peritoneum is a membranous lining of the abdominal body cavity that due to a large number of blood vessels and capillaries is capable of acting as a natural semi-permeable membrane.
In continuous ambulatory peritoneal dialysis, a dialysis solution is introduced into the peritoneal cavity utilizing a catheter. Solutes (e.g., urea, creatinine etc.) diffuse from the blood into the dialysate due to the presence of a diffusion gradient. Similarly, the presence of an osmotic gradient between the peritoneal cavity and the blood causes fluid to be removed from the body into the dialysate which is then drained through the catheter. These processes allow the proper chemical and fluid balance to be returned to the body. After a sufficient period of time, an exchange of solutes between the dialysate and the blood is achieved. Fluid removal is achieved by providing a suitable osmotic gradient from the blood to the dialysate to permit water out flow from the blood. This allows the proper acid-base, electrolyte and fluid balance to be returned to the blood and the dialysis solution is simply drained from the body cavity through the catheter.
Peritoneal dialysis raises a number of issues including: the danger of peritonitis; a lower efficiency and therefore increased duration of dialysis hours compared to hemodialysis; and cost issues when automated equipment is utilized.
A number of variations on peritoneal dialysis have been explored. One such variation is reciprocating, recirculating, or semi-continuous peritoneal dialysis. In such systems, dialysis solution is infused into the peritoneal cavity and then, typically, on a continuous process basis a portion of the dialysis solution is sequentially drained, cleansed, and reinfused.
FIG. 1 illustrates early work performed by Shinaberger et al, in this area that is discussed in "Increasing Efficiency of Peritoneal Dialysis: Experience with Peritoneal-Extracorporeal Recirculation Dialysis", Trans Amer Soc Artif Int Organs 11 (1965): 76-82. As illustrated in FIG. 1, both an inflow 10 and outflow 12 catheter are utilized to produce a continuous single direction of dialysate flow. Sterile dialysate, which is purified by passage through a coil dialyzer 14 that is bathed in a 100 liter non-sterile dialysis bath, flows through the inflow catheter 10 and into the peritoneum. The dialysate then flows out of the peritoneum through the outflow catheter 12.
Further, work in this area in humans is disclosed in Stephen et al, "Recirculating Peritoneal Dialysis with Subcutaneous Catheter," Transactions ASAIO 22 (1976): 575-585. Gordon, A. et al, "Augmentation of Efficiency by Continuous Flow Sorbet Regeneration Peritoneal Dialysis", Trans Amer Soc Artif Int Organs, XXII (1976): 599-605, discloses further work in this area in dogs.
One disadvantage with the system of Shinaberger et al is that it requires the use of two catheters. Each catheter represents a separate exit site and possibility for infection.
Accordingly, one of the goals of further work in this area was the elimination of one of the catheters. Di Paolo in "Acceleration of Peritoneal Dialysis With Single Device", Nephron, 19: 271-277 (1977) discloses a single needle system. FIG. 2 illustrates the system of Di Paolo. A single needle 20 is used to infuse fluid from the sterile reservoirs 24, 26 into the patient where it dwells and then subsequently flows to drain 28. Inflow into the patient is achieved through a pump 30, while outflow is achieved by gravity.
U.S. Pat. No. 4,190,047 discloses a single catheter system that utilizes two pumps to alternate inflow and outflow of dialysate fluid. During the outflow cycle, fluid is passed through the blood path of the dialyzer where it is "cleaned" prior to the next in flow.
FIG. 3 sets forth a figure from U.S. Pat. No. 5,141,493. FIG. 3 illustrates the three loop system of the '493 patent wherein dialysate is reciprocated into and out of the patient using a reversible pump (first loop) into a second loop. In the second loop, the dialysate passes through a dialyzer being regenerated by non-sterile dialysate flowing in the third loop. The difference between this system and earlier systems is that both regeneration and reciprocation are continuous.
All of the above investigators have reported increased small molecule clearance and higher ultrafiltration with either a continuous flow or reciprocating type system. This is an advantage that is desirable. However, these systems are quite complex in their operation, set-up, and control. There is therefore a need for an improved peritoneal dialysis system based on a reciprocating, recirculating, or semi-continuous dialysis method.